Conventionally, an amplifier circuit having an operational amplifier is known as an amplifier circuit to amplify an analog signal by a predetermined amplification factor. In the amplifier circuit having an operational amplifier, virtual ground voltage of the operational amplifier approaches an ideal value as the gain of the operational amplifier becomes larger, which leads to the improvement of amplification accuracy. However, in recent years, the development of miniaturization of CMOS devices has made it difficult to design an operational amplifier having a high gain. This leads to a problem that an amplification error occurs depending on an error occurring in the virtual ground voltage of the operational amplifier.
Further, an amplifier circuit having a comparator instead of the operational amplifier has been proposed. However, the amplifier circuit having a comparator has a problem that an amplification error occurs depending on the finite delay of the comparator.